Seasonal Variability and Governing Mechanisms of Upper-Ocean Submesoscale Processes in the South China Sea, East of Viet Nam

This study systematically analyzed the seasonal variability and regulating mechanisms of upper-layer submesoscale processes in the South China Sea, east of Viet Nam based on the high-resolution ocean model OFES (Ocean general circulation model for the earth simulator) simulations from January 2001 to December 2003. The findings reveal active submesoscale processes in the upper layer of this sea region, exhibiting significant regional-dependent seasonal variations. In the northern area (13°N—17°N, 110°E—117°E), submesoscale processes are stronger in winter and weaker in summer. In contrast, in the southern area (5°N—11°N, 108°E—116°E), these processes are stronger in summer and autumn, and weaker in winter and spring. Further analysis suggests that the seasonal variations of submesoscale processes in both areas are jointly influenced by frontogenesis and baroclinic instability. The release of available potential energy due to submesoscale vertical buoyancy work is a key energy source for these processes in both regions. Notably, in the northern area, submesoscale processes can transfer kinetic energy to larger-scale processes through nonlinear interactions, thus exerting a certain regulatory effect on the kinetic energy of mesoscale and large-scale processes.